Priming device for spillway siphons



9, 1924. I 1,518,489 P. .DAVIES I PRIMING DEVICE FOR SPILL-WAY SIPHONSFiled March 6, 1923 l/l/I/IIIIII/[ IIIIIIIIIIIIIIIIIIIIJIIII I, III,

INVENTOR WITNESSES Patented Dec. 9, 1924.

UNITED STATES POWYS DAVIES, 0F RAIPUR, INDIA.

PRIMING DEVICE FOR SPILLWAY SIPI-IONS.

Application filed March 6,

To all whom it may concern:

Be it known that I, vPowrs DAVIES, a subject of the King of England,residing at Raipur, Central Provinces, India, executive engineer andsuperintendent of works in the public works department of India, haveinvented certain new and useful Improved Priming Devices for SpillwaySiphons, of which the following is a specification.

In the ordinary spillway siphon, priming is secured by a rise ofwater-level in the reservoir or canal which causes water to spill overthe crest of the siphon; air is carried out of the siphon by the fallingwater and, owing to the resulting partial vacuum formed, the water risesin the siphon and the priming action is intensified until the siphon isrunning full within one or more minutes. The device according to thisinvention, enables a powerful jet of water to be projected into the mainsiphon by means of a relatively smaller siphon (or siphons) of similargen e a1 construction which is built or provided in the over-pour crestwall of the main siphon; this small siphon, hereinafter called the babysiphon to distinguish it from the main siphon, in brief, enables themain siphon to be primed with a smaller risein water level in thereservoir or canal and thereby permits of closer regulation ofwater-level in the said reservoir or canal. Secondly it makes itpossible to dispense with the downstream seal in the largest siphons andstill secure priming with a moderate rise of water level in the saidreservoir or canal and thus very materially to increase the dischargingcapacity of the siphons. Thirdly it makes it possible by constructing avery small siphon in the crest of the baby siphon itself to securepriming of the largest siphons both with an almost negligible rise ofwater level in the said reservoir or canal andwith no downstream seal inthe main siphon and thereby permits of both close regulation and greatlyi11- creased discharging capacity.

In order that my said invention may be clearly understood and readilycarried into effect, the same will now be described more fully, by wayof example, with reference tothe accompanying drawings, in which Figure1 is a vertical section of a device embodying the invention, and

Figure 2 is a similar view to Figure 1 but showing a modification.

Referring first more particularly to Fig- 1923. Serial No. 623,119;

ure 1, the device shown enables a powerful jet of water to be projectedinto the main siphonby means'of a relatively small or baby siphonconstructed or provided in the over-pour crest wall, by which means agiven rise in water-level in the reservoir or canal will have the sameeffect in priming the siphon as many times such rise in waterlevel whenpriming depends on flow over the crest alone. When the main siphon isprovided with a downstream seal the baby siphon will be of very smalldimensions and an almost negligible rise of water level in the reservoirwill secure priming of the main siphon but when the main siphon has nodownstream seal as in the construction shown in Figure 1 the baby siphonmust be made of substantial size depending on the size of the mainsiphon which it has to prime. It will be observed that the crest of thesiphon is sloped from A to B the object being to throw across the siphonthis stream of water passing over the crest during the action of primingand thereby to ensure that such stream will not depress the jet from thebaby siphon vertically downwards inside the siphon, which action wouldcause air to be admitted into the siphon fromthe bottom C and therebyprevent full priming.

The adoption of this device increases the discharging capacity of themain siphon very greatly, partly owing to the omission of the downstreamseal and partly owing to the fact that the discharge through the babysiphon itself is added to that of the main stream.

In cases where the maximum discharging capacity combined with very closeregulation of the water-level of the reservoir or canal is required thedesign will be as shown in Figure 1 with the exception that in this casethe baby siphon itself will be provided, as shown in Figure 2 with asimilar but still smaller siphon, as D, which is primed by a slightincrease in the reservoir waterlevel and in turn primes the baby siphonwhich likewise in its turn primes the main siphon. For instance, whenthe water in the reservoir rises sufficiently to seal the upstream sideof the siphons, water pours over the crest of the smallest siphon andcauses it to prime. The smallest siphon discharges into the medium sizedsiphon and causes it to prime in turn. The latter then discharges intothe main siphon and causes it to prime in the same way. A verysmall'rise of water level above the crest of the smallest siphon issuiiicient to prime it so that by the operation of all these siphonsworkingj'in turn, the largest siphon can be primed With a very smallrise of Water levelin the reservoir.

The baby siphon Will ordinarily be constructed of reinforced concreteand the Very smallsiphon in the crest of the baby siphon will ordinarilybe of suitable metal but Ido not confine myself to this particularmethod able method.

What I claim is 1. A' spillway siphon having a siphonor siphons,"relatively smaller than the'main siphon, provided in the over-pourcrest'wall substantially 'asand for the purpose hereinbefore described.

the outlet legof the main siphon and having its outlet leg and suctionend arranged externally ofthepassage through the main siphon, the outletendof the said smaller siphon extending the full Width of the mainlSlPllOll'ttl'lCl being so adapted as to cause a of construction but mayuse'any other su1t-" stream of Water or other liquid to be projected' toefiect the sealing 'ofthe outlet leg of the main siphon.

In test mony whereof I have hereunder P. DAVIES.

signed my name.

